Atomistic dynamics simulation to solve conformation of model PCE superplasticisers in water and cement pore solution

The working mechanism of polycarboxylate ether (PCE) type superplasticisers in concrete was studied from the point of view of conformational changes of the polymer simulated by molecular dynamics in pure water and cement pore solution. Three typical types of PCEs, namely a methoxy polyethyleneglycol monomethacrylate-sodium methacrylate copolymer (PCEM), a polyethyleneglycol mono allyl ether-sodium maleate copolymer (PCEA) and a polyethyleneglycol mono (3-methyl-3-butenyl) ether-sodium acrylate copolymer (PCEI) were investigated using large-scale atomistic molecular dynamics simulations. It was observed that the PCE polymers which possess negatively charged backbones were stretched in water due to electrostatic repulsion. However, they were found to be significantly shrunken and distorted in synthetic cement pore solution, depending on the polyethylene glycol (PEG) density along the backbone, resulting in the aggregation of PEG side chains due to the salting-out effect.